Plant artificial chromosome platforms via telomere truncation

Abstract

The invention provides engineered plant minichromosomes generated by telomere mediated truncation of native chromosomes. These minichromosomes are faithfully transmitted from one generation to the next and provide an ideal platform for breeding genes into desired plant varieties with out problems, such as linkage drag, associated with standard breeding methods.

What is claimed is: 
     
       1. A plant minichromosome produced by telomere-mediated truncation of one or both arms of a starting plant chromosome, wherein the minichromosome comprises heterologous engineered telomere sequences and a native plant centromere and is stably transmitted during mitosis and meiosis in a plant comprising the minichromosome that is of the same species as the plant from which the starting plant chromosome was obtained. 
     
     
       2. The plant minichromosome of  claim 1 , wherein about 25% to about 99.9% of the starting plant chromosome has been truncated. 
     
     
       3. The plant minichromosome of  claim 1 , wherein the heterologous engineered telomere sequences comprise about 2 to 100 telomere repeats. 
     
     
       4. The plant minichromosome of  claim 3 , wherein the heterologous engineered telomere sequences comprise about 6 telomere repeats. 
     
     
       5. The plant minichromosome of  claim 1  , wherein the heterologous engineered telomere sequences are from  Arabidopsis.    
     
     
       6. The plant minichromosome of  claim 1 , wherein both arms of the starting plant chromosome have been truncated. 
     
     
       7. The plant minichromosome of  claim 1 , wherein the minichromosome is from about 1 Mb to about 100 Mb in size. 
     
     
       8. The plant minichromosome of  claim 1 , wherein the starting plant chromosome is an A chromosome. 
     
     
       9. The plant minichromosome of  claim 1 , wherein the starting plant chromosome is a B chromosome. 
     
     
       10. The plant minichromosome of  claim 1 , wherein the starting plant chromosome is from a dicot. 
     
     
       11. The plant minichromosome of  claim 10 , wherein the starting plant chromosome is from a monocot. 
     
     
       12. The plant minichromosome of  claim 11 , wherein the starting plant chromosome is from maize. 
     
     
       13. The plant minichromosome of  claim 1 , further comprising a site-specific recombination site. 
     
     
       14. The plant minichromosome of  claim 13 , wherein the site-specific recombination site is an FRT or lox site. 
     
     
       15. The plant minichromosome of  claim 1 , further comprising a transgene. 
     
     
       16. The plant minichromosome of  claim 15 , wherein the transgene confers a trait selected from the group consisting of insect resistance, herbicide tolerance, altered carbohydrate metabolism, altered fatty acid metabolism, disease resistance, male fertility restoration and pest resistance. 
     
     
       17. A plant cell comprising the plant minichromosome of  claim 1 . 
     
     
       18. A plant comprising the plant minichromosome of  claim 1 . 
     
     
       19. The plant of  claim 17 , wherein the plant is maize. 
     
     
       20. A seed comprising the plant minichromosome of  claim 1 . 
     
     
       21. A method of producing a plant minichromosome, comprising the steps of:
 (a) transforming a starting plant chromosome with a heterologous nucleic acid comprising at least two telomere repeat sequences; and 
 (b) allowing telomere-mediated truncation of the starting plant chromosome to occur to produce a plant minichromosome. 
 
     
     
       22. The method of  claim 21 , further comprising transforming the starting plant chromosome with a site-specific recombination site. 
     
     
       23. The method of  claim 21 , wherein the site-specific recombination site is an FRT or lox site. 
     
     
       24. The method of  claim 21 , wherein the telomere repeat sequences are from  Arabidopsis.    
     
     
       25. The method of  claim 21 , wherein the heterologous nucleic acid comprises about 6 telomere repeat sequences. 
     
     
       26. The method of  claim 21 , wherein the starting plant chromosome is transformed by  Agrobacterium -mediated transformation. 
     
     
       27. The method of  claim 21 , wherein the starting plant chromosome is transformed by DNA bombardment. 
     
     
       28. The method of  claim 21 , wherein both arms of the starting plant chromosome are truncated. 
     
     
       29. The method of  claim 21 , wherein the starting plant chromosome is an A chromosome. 
     
     
       30. The method of  claim 21 , wherein the starting plant chromosome is a B chromosome. 
     
     
       31. The method of  claim 21 , further comprising transforming the starting plant chromosome with a selected coding sequence. 
     
     
       32. The method of  claim 21 , wherein the selected coding sequence confers a trait selected from the group consisting of insect resistance, herbicide tolerance, altered carbohydrate metabolism, altered fatty acid metabolism, disease resistance, male fertility restoration and pest resistance. 
     
     
       33. The method of  claim 21 , wherein the starting plant chromosome is comprised in a plant cell. 
     
     
       34. The method of  claim 33 , wherein the plant cell comprises at least 2 B chromosome copies. 
     
     
       35. The plant cell of  claim 17 , wherein the plant minichromosome comprises a transgene. 
     
     
       36. The method of  claim 21 , wherein the starting plant A chromosome is transformed by  Agrobacterium -mediated transformation. 
     
     
       37. The method of  claim 21 , wherein the starting plant B chromosome is transformed by microprojectile bombardment. 
     
     
       38. The plant minichromosome of  claim 16 , wherein the coding sequence conferring male fertility restoration is a Rf3 gene. 
     
     
       39. The method of  claim 32 , wherein the coding sequence conferring male fertility restoration is a Rf3 gene.